【Epitaxy Papers】Structural and electronic modification in β-Ga₂O₃ thin films induced by hafnium incorporation

      Researchers from United Arab Emirates University have published a dissertation titled " Structural and electronic modification in β-Ga₂O₃ thin films induced by hafnium incorporation " in Applied Surface Science.

Abstract

      The impact of hafnium (Hf) incorporation on the structural, chemical, and electronic properties of β-Ga₂O₃ thin films was investigated. Hf-Ga₂O₃ thin films were prepared by the co-sputtering technique with Hf concentrations ranging from 0 to 17 atomic percent (at.%). Grazing incidence X-ray diffraction analysis revealed a composition-dependent phase transition. At low Hf concentrations (0–4.5 at.%), substitutional incorporation disrupted the β-Ga₂O₃ lattice and reduced crystallinity. Whereas high Hf concentrations (9–17 at.%) induced phase separation, yielding crystalline m-HfO₂–β-Ga₂O₃ nanocomposites. Optical spectroscopy showed bandgap narrowing from 4.62 to 4.30 eV at low doping levels due to impurity band formation, followed by widening to 5.07 eV at higher Hf content. X-ray photoelectron spectroscopy confirmed Hf incorporation within the oxide structure and revealed upward band bending (1.35–2.89 eV) with a depletion layer width of 38–56 nm. Heavily doped films may alternatively be interpreted as Ga-doped m-HfO₂, where Ga reduces the bandgap and upward band bending relative to pure m-HfO₂. This dual perspective underscores the potential of the Hf-Ga₂O₃ system for tailoring surface electronic properties in advanced device applications.

DOI：

https://doi.org/10.1016/j.apsusc.2026.167137